test(performance): count startup phases and SQL statements for the J1 launch journey

Implements plan item A2. With IPTVNATOR_PERF_CAPTURE=1 the main process
keeps named counters and registers a main-only performance:read-counters
IPC handler; without the flag nothing is counted and the handler does not
exist.

- debug-trace.ts owns the registry; traceStartupPhase replaces the
  trace('startup', ...) sites and counts main.startupPhases.
- The database worker counts executed statements through better-sqlite3's
  Statement prototype (the verbose callback expands every statement and
  made bulk inserts 2-4x slower) and posts the count over its message
  port, flushed before every other worker message. The main-thread shared
  connection is counted through a new connection observer in the shared
  database library.
- The first main window freezes main.modulesRegisteredBeforeWindow at
  creation and main.sqlStatementsBeforeReadyToShow at ready-to-show.
- The journey gate drops the ready-to-show that Electron emits for the
  about:blank detour, so the app sees the real document's first paint,
  and taps the counters handler; the J1 record reads both counters after
  the renderer probe completes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libs/shared/database/README.md

@@ -28,6 +28,9 @@ import { content, categories, playlists, type Content } from '@iptvnator/shared/
 - `closeDatabase()` - Close connection
 - `getDatabasePath()` - Get database file path
 
+### Connection observer (`connection-observer.ts`)
+- `setDatabaseConnectionObserver(observer | null)` - Called by `initDatabase` with each connection it opens, before any statement runs on it. The Electron main process registers one only with `IPTVNATOR_PERF_CAPTURE=1`, to count main-thread SQL statements. The module has no runtime dependencies and is also importable as `@iptvnator/shared/database/connection-observer`.
+
 ## Database Location
 
 The SQLite database is stored at: `~/.iptvnator/databases/iptvnator.db`